1. Field of the Invention
Embodiments of the invention relate generally to the field of computer systems. More particularly, embodiments of the invention relate to an access control mechanism for non-volatile random access memory in a computer system.
2. Description of the Related Art
In conventional computer systems, system memory (also known as main memory, primary memory, executable memory) is typically implemented by dynamic random access memory (DRAM). DRAM-based memory consumes power even when no memory reads or writes occur because it constantly recharges internal capacitors. DRAM-based memory is volatile, which means data stored in DRAM memory is lost once the power is removed. For many computer systems, especially mobile platforms, power utilization is a critical issue in terms of cost and performance.
Phase-change memory (PCM), also sometimes referred to as phase change random access memory (PRAM or PCRAM), PCME, Ovonic Unified Memory, or Chalcogenide RAM (C-RAM), is a type of non-volatile computer memory which exploits the unique behavior of chalcogenide glass. As a result of heat produced by the passage of an electric current, chalcogenide glass can be switched between two states: crystalline and amorphous. Recent versions of PCM can achieve two additional distinct states. As a result, storage density and capacity are significantly increased.
PCM provides higher performance than flash memory (also referred to as “flash”) because the memory element of PCM can be switched more quickly, writing (changing individual bits to either 1 or 0) can be done without the need to first erase an entire block of cells, and degradation from writes is slower (a PCM device may survive approximately 100 million write cycles; PCM degradation is due to thermal expansion during programming, metal (and other material) migration, and other mechanisms).